In general a fluorine-containing resin inherently possesses thermal resistance, chemical resistance and low coefficient of friction, and for purposes to further improve mechanical characteristics and abrasion resistance, trials to add an inorganic or organic filler have been made.
However a fluorine-containing polymer itself has low surface energy and poor dispersibility when mixed with a filler, and the addition of the filler has insufficient effect on mechanical characteristics of the polymer. Also interfacial adhesion between the fluorine-containing polymer and the filler in the mixture is poor. For example, in case of use for a sliding material, the filler in a molded article is easily released from the sliding surface. Thus enough effect on abrasion resistance cannot be obtained and a sliding material having a long life has not been produced.
For the purpose to improve interfacial adhesion between the fluorine-containing resin and the filler, trials to admix a filler which is previously surface-treated with an organic compound have been made.
Various prior arts in which silane compounds are used as a surface-treating agent have been disclosed. For example, a hydrolyzable non-fluorine-containing siloxane compound having terminal amine group is used for surface-treating of glass fiber (U.S. Pat. No. 3,787,281), a silane coupling agent having methyl group bonded with silicon atom is used for surface-treating of a filler (JP-A-7-53780) and a fluorine-containing silane coupling agent such as: ##STR1##
is used (JP-A-4-272973).
Also there have been disclosed use of a fluorine-containing acid chloride for surface-treating of a glass fiber and carbon fiber (JP-A-4-345691), use of fluoropolyether having, at its molecular end, a functional group such as a siloxane group, alkoxy titanium group, epoxy group or isocyan group for surface-treating of a reinforcing material (JP-B-7-64973), etc.
Since those surface-treating agents basically differ from the fluorine-containing ethylenic polymer which is a matrix component from structural point of view, interfacial adhesion between the fluorine-containing polymer and the filler in the composition prepared by mixing the filler surface-treated by the mentioned methods or in the molded article is not enough, and the addition of such a filler does not have sufficient effect on mechanical characteristics and abrasion resistance of the molded article.
Also many of those surface-treating agents are generally insufficient in thermal resistance and chemical resistance, thus causing foaming and coloring due to decomposition of the surface-treating agent at the time of kneading and molding of the fluorine-containing resin and surface-treated filler. For example, in case of the uses for molded parts, which require thermal durability, among structural materials and sliding materials in the fields of automobiles, industrial machineries, OA apparatuses, domestic electric appliances, etc., there occurs elusion of the surface-treating agent or decomposed product thereof, which lowers initial characteristics (mechanical properties and abrasion resistance).
An object of the present invention is to solve the above-mentioned problems and to provide a resin composition which can give characteristics such as excellent mechanical properties and abrasion resistance to a molded article, while maintaining excellent thermal resistance, chemical resistance, surface characteristics (non-sticking property, low friction property), electrical insulating property and the like of the fluorine-containing polymer. Other objects are to provide a molded article produced from the resin composition and to provide a method for producing the molded article.